The present invention is related to a pressure locking filler cap for a vessel or container, and more particularly to a locking filler cap which interferes with an operator's ability to connect a turning tool to the cap under unsafe pressure conditions.
Locking filler caps are commonly provided over the openings in pressurized vessels or tanks through which such vessels can be refilled. It may be hazardous to open the filler cap while the vessel is still pressurized. As the filler cap is being removed, e.g. unscrewed, it could explode from the vessel upon final thread disengagement or permit explosive or too rapid exit of the contents of the vessel and cause injury to personnel and to property.
The prior approach to preventing opening of the filler cap before the internal pressure of its vessel is relieved was to either warn the operator of the high pressure condition or to interfere with the opening of the filler cap. Known warning schemes include prominently located labels on the vessel and on the filler cap, pressure gauges to indicate actual tank pressure near the filler cap, deliberate creation of a high thread engagement force for a screw cap under pressurized conditions so as to interfere with removal of the cap, and vent holes or the like for producing an air pressure induced audible response if the cap is loosened while the vessel is still pressurized.
Several U.S. patents disclose vessel caps with a mechanism that will interfere with unscrewing of the cap unless the internal pressure of the vessel is first relieved.
U.S. Pat. No. 1,858,013 to Heins discloses a cap which is retained in place by a threaded element 17 which may be turned by a handle 69. Under pressure, a rod 52 is pushed outwardly whereby, with the cooperation of a pin 48 and a member 45, cooperating screw teeth 22 and 74 are separated so that turning of the handle does not produce any turning of the threaded elements of the filler cap.
Dunton, U.S. Pat. No. 2,670,099, discloses a bolt-shaped cover wherein, as seen from FIGS. 7 and 8, an internal pressure communicates through an axially extending port 54 to act against a piston 62 to thereby disengage a turning rod 58 from a groove 90. In a disengaged position, rod 58 is uncoupled from the bolt and is not usable for turning or unscrewing the bolt until the pressure is relieved.
U.S. Pat. No. 1,706,051 to Auchincloss provides a piston that under pressure causes threads of a cover to lock to prevent the disengagement thereof.
Guiver, U.S. Pat. No. 3,122.263, discloses a pipe plug 1 having a stiff end anc a movable plunger 18. Pressure within the pipe moves the plunger outwardly to lock a bolt 12 in a groove in the pipe thereby preventing its removal by a grab mechanism that engages the internal flanges 27 on the outer end of the sleeve.
Wackman, U.S. Pat. No. 1,891,033, takes a different approach by providing a top cover 16 which is snap mounted onto the cap to cover a wrench receiving socket in the cap. The cap cover cannot be removed before the seal is broken.